The disclosure is generally related to a battery voltage detector, and specifically to a battery voltage detector detecting an output of a connectable DC (Direct Current) power supply.
Japanese Patent No. 4169173 (prior art document 1) discloses a voltage detection circuit that is connected via a switch when the output voltage becomes higher than a reference voltage, and detects an overvoltage with a comparator using voltage-dividing resistors. In this voltage detection circuit, a DC-DC converter 10 converts DC input voltage Vin into DC voltage V0 having a different voltage value, and supplies it to output terminals 8 and 9. A control circuit 11 controls the DC-DC converter 10. An overvoltage protection circuit 12 detects DC output voltage V0 supplied to the output terminals 8 and 9 to generate voltage detection signal V1, also compares voltage detection signal V1 and reference voltage signal Vr1 to generate overvoltage detection signal V2, and supplies overvoltage detection signal V2 to the control circuit 11. A switch unit 2B, operating simultaneously with a power-on switch 2A, opens and closes an electrical circuit formed between the output side of the DC-DC converter 10 and the overvoltage protection circuit 12.